Soft porous materials of metals or metal alloys are well known, however, the area of utilization of these materials is limited and utilization in the area of brazing is not developed at all.
Manufacturing methods of porous materials of metals or metal alloys are mentioned in Japanese Patent Laying Open Publication Number Heisei 5-339605, Japanese Patent Laying Open Publication Number Heisei 6-158116, Japanese Patent Laying Open Publication Number 2003-328006, and Japanese Patent Laying Open Publication Number 2003-328007 etc. Most of these porous materials have softness. Softness here means that the material is fiber type like cotton and that the thickness of the material is freely adjusted by pressure.
However utilization of these porous materials is not known in the area of brazing.
In brazing sometimes the opening thickness between the materials being brazed, which might be metals, metal alloys, ceramics etc., can not be kept constant. In other words, the opening might be rather large, or the shape of the materials being brazed might not be ordinary, or the number of parts to be brazed is more than two or larger. In these cases it is very difficult to keep bonding opening constant even if using holding tools, and consequently it is impossible to have good brazing. Also it is impossible to have good brazing when the opening thickness between the materials being brazed is rather larger than the proper opening thickness 0-0.05 mm indicated in Brazing Handbook (AWS) 1991, for example, the opening thickness is more than 0.1 mm.
It is important to have the proper bonding opening because the liquid solder is inserted into the bonding opening and then bonding is done by curing the melted solder. This is the basis of brazing. When the bonding opening is bigger as mentioned above, liquid solder can not be inserted and held in between.